A live attenuated strain of Yersinia pestis KIM as a vaccine against plague

• Published in: Vaccine 2011-04, Vol.29 (16), p.2986-2998
• Main Authors: Sun, Wei, Six, David, Kuang, Xiaoying, Roland, Kenneth L, Raetz, Christian R.H, Curtiss, Roy
• Format: Article
• Language: English
• Subjects: Acyltransferases - genetics; Acyltransferases - immunology; Administration, Intranasal; agonists; Allergy and Immunology; Animals; Antibodies, Bacterial - blood; Applied microbiology; Bacterial diseases; Bacteriology; Biological and medical sciences; bioterrorism; chromosomes; Cytokines - immunology; Escherichia coli; Escherichia coli Proteins - genetics; Escherichia coli Proteins - immunology; Female; Fundamental and applied biological sciences. Psychology; Human bacterial diseases; immunization; Infectious diseases; Injections, Subcutaneous; innate immunity; lethal dose 50; Lipid A; Lipid A - immunology; Medical sciences; Mice; Microbiology; Miscellaneous; mutants; mutation; Plague; Plague - immunology; Plague - pathology; Plague - prevention & control; Plague vaccine; Plague Vaccine - genetics; Plague Vaccine - immunology; Plasmids; Promoter Regions, Genetic; Regulated delayed attenuation; temperature; Toll-like receptor 4; Tropical bacterial diseases; vaccine development; vaccines; Vaccines, antisera, therapeutical immunoglobulins and monoclonal antibodies (general aspects); Vaccines, Attenuated - genetics; Vaccines, Attenuated - immunology; Virulence; Yersinia pestis; Yersinia pestis - genetics; Yersinia pestis - immunology; Yersinia pestis - pathogenicity
• ISSN: 0264-410X; 1873-2518
• DOI: 10.1016/j.vaccine.2011.01.099

Abstract Yersinia pestis , the causative agent of plague, is a potential weapon of bioterrorism. Y. pestis evades the innate immune system by synthesizing tetra-acylated lipid A with poor Toll-like receptor 4 (TLR4)-stimulating activity at 37 °C, whereas hexa-acylated lipid A, a potent TLR4 agonist, is made at lower temperatures. Synthesis of Escherichia coli LpxL, which transfers the secondary laurate chain to the 2′-position of lipid A, in Y. pestis results in production of hexa-acylated lipid A at 37 °C, leading to significant attenuation of virulence. Previously, we described a Y. pestis vaccine strain in which crp expression is under the control of the arabinose-regulated araC PBAD promoter, resulting in a 4–5 log reduction in virulence. To reduce the virulence of the crp promoter mutant further, we introduced E. coli lpxL into the Y. pestis chromosome. The χ10030(pCD1Ap) (Δ lpxP32 ::PlpxL lpxL ΔPcrp21 ::TT araC PBAD crp ) construct likewise produced hexa-acylated lipid A at 37 °C and was significantly more attenuated than strains harboring each individual mutation. The LD50 of the mutant in mice, when administered subcutaneously or intranasally was >107 -times and >104 -times greater than wild type, respectively. Mice immunized subcutaneously with a single dose of the mutant were completely protected against a subcutaneous challenge of 3.6 × 107 wild-type Y. pestis and significantly protected (80% survival) against a pulmonary challenge of 1.2 × 104 live cells. Intranasal immunization also provided significant protection against challenges by both routes. This mutant is an immunogenic, highly attenuated live Y. pestis construct that merits further development as a vaccine candidate.